1. Field of the Invention
The present invention relates to alkaline storage batteries.
2. Description of the Related Art
In recent years, alkaline storage batteries have been used as power sources for portable information equipment such as cellular phones and notebook computers, electric cars, or hybrid vehicles, and there has been a demand for high performance, in particular long life of alkaline storage batteries. In particular, for batteries for electric cars, it is considered that they are left unused for a long time, so that in order to prevent the start-up properties of an engine from deteriorating after being left unused, there is a strong demand for batteries with little self-discharge.
On the other hand, in alkali storage batteries such as nickel/metal-hydride (Ni/MH) storage batteries, self-discharge is suppressed by performing a specific treatment for providing hydrophilicity such as a sulfonation treatment with respect to a separator (e.g., JP 1-132044 A).
However, for use in a power source of an electric car, self-discharge should be suppressed further. In addition, the costs of sulfonation treatment are high.
On the other hand, as a method for providing hydrophilicity at low cost, and corona discharge is used, for example. However, this method has a problem in that the self-discharge characteristics are poorer that those of a separator that has been subjected to a sulfonation treatment.